如何获得当前的前台活动的上下文中的android？ [英] How to get current foreground activity context in android?

问题描述

每当执行我广播我想告诉警惕前台活动。

Whenever my broadcast is executed I want to show alert to foreground activity.

推荐答案

（注意：一个官方的API中添加了API 14：看到这个答案<一个href="http://stackoverflow.com/a/29786451/119733">http://stackoverflow.com/a/29786451/119733)

(Note: An official API was added in API 14: See this answer http://stackoverflow.com/a/29786451/119733)

不要使用preVIOUS（waqas716）的答案。

DO NOT USE PREVIOUS (waqas716) answer.

您将有因为静态引用到活动的内存泄漏问题。欲了解更多详细信息请访问以下链接<一个href="http://android-developers.blogspot.fr/2009/01/avoiding-memory-leaks.html">http://android-developers.blogspot.fr/2009/01/avoiding-memory-leaks.html

You will have memory leak problem, because of the static reference to the activity. For more detail see the following link http://android-developers.blogspot.fr/2009/01/avoiding-memory-leaks.html

要避免这种情况，你应该管理活动的参考。 添加应用程序的名称清单文件中：

To avoid this, you should manage activities references. Add the name of the application in the manifest file:

<application
    android:name=".MyApp"
    ....
 </application>

您的应用程序类：

  public class MyApp extends Application {
        public void onCreate() {
              super.onCreate();
        }

        private Activity mCurrentActivity = null;
        public Activity getCurrentActivity(){
              return mCurrentActivity;
        }
        public void setCurrentActivity(Activity mCurrentActivity){
              this.mCurrentActivity = mCurrentActivity;
        }
  }

创建一个新的活动：

Create a new Activity :

public class MyBaseActivity extends Activity {
    protected MyApp mMyApp;

    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        mMyApp = (MyApp)this.getApplicationContext();
    }
    protected void onResume() {
        super.onResume();
        mMyApp.setCurrentActivity(this);
    }
    protected void onPause() {
        clearReferences();
        super.onPause();
    }
    protected void onDestroy() {        
        clearReferences();
        super.onDestroy();
    }

    private void clearReferences(){
        Activity currActivity = mMyApp.getCurrentActivity();
        if (this.equals(currActivity))
            mMyApp.setCurrentActivity(null);
    }
}

所以，现在，而不是为你的活动扩展Activity类，只是扩展MyBaseActivity。现在，你可以从应用程序或活动的情况下一样，让你的当前活动：

So, now instead of extending Activity class for your activities, just extend MyBaseActivity. Now, you can get your current activity from application or Activity context like that :

Activity currentActivity = ((MyApp)context.getApplicationContext()).getCurrentActivity();

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